This invention relates to a microwave enhanced CVD method for depositing a boron nitride or a boron nitride in combination with carbon.
Recently, ECR CVD has attracted the interests of researchers as a new method of manufacturing thin films, particularly amorphous thin films. For example, Matsuo et al discloses one type of such an ECR CVD apparatus in U.S. Pat. No. 4,401,054. This recent technique utilizes microwaves to energize a reactive gas into a plasma state by virtue of a magnetic field which functions to pinch the plasma gas within the excitation space. With this configuration, the reactive gas can absorb the energy of the microwaves. A substrate to be coated is located distant from the excitation space (resonating space) for preventing the same from being spattered. The energized gas is showered on the substrate from the resonating space. In order to establish an electron cyclotron resonance, the pressure in a resonating space is kept at 1.times.10.sup.-3 to 1.times.10.sup.-5 Torr at which electrons can be considered as independent particle and resonate with a microwave in an electron cyclotron resonance on a certain surface on which the magnetic field takes a particular strength required for ECR. The excited plasma is extrated from the resonating space, by means of a divergent magnetic field, to a deposition space which is located distant from the resonating space and in which is disposed a substrate to be coated.
In such a prior art method, it is very difficult to form a thin film of a polycrystalline or single-crystalline structure, so that currently available methods are almost limited to processes for manufacturing amourphous films. Also, high energy chemical vapor reaction is difficult to take place in accordance with such a prior art and therefore a diamond film or other films having high melting points, or uniform films on an even surface having depressions and caves can not be formed.
Furthermore, it was impossible to coat the surface of a super hard metal such as tungsten carbide with a carbon film. Because of this, it is required to coat a super hard surface with a fine powder of diamond for use of abrasive which has a sufficient hardness and to make sturdy mechanical contact between the diamond powder and the substrate surface.